US scientists are creating novel life forms: “human pig chimeras”. These are a blend of human and pig characteristics. They are like mules who will provide organs to us. A mule is the offspring of a male donkey (jack) and a female horse (mare). Horses and donkeys are different species, with different numbers of chromosomes but they can breed together.

In this case, they take a skin cell from a person and turn it back in time to make stem cells capable of producing any cell or tissue in the body, “induced pluripotent stem cells.” They then inject this into a pig embryo. This makes a pig human chimera.

However they do a modification to the pig embryo first. They use gene editing, or CRISPR, to knock out the pig’s genes which produce an organ, say the pancreas. The human stem cells for the pancreas then make an almost entirely human pancreas in the pig human chimera. It functions like an organ mule. (The blood vessels are still porcine.)

In this way, your skin cell could grow a new liver, heart, pancreas, or lung.

This is a technique with wider possibilities: other US teams are working on a chimera –based treatment, this time for Parkinson’s disease which will use chimeras to create human neurones.

CRISPR is also credited with enhancing the safety of this technique, with the BBC reporting that a Harvard team were able to use the new and revolutionary technique to remove copies of a pig retrovirus.

Safety is always a major concern when science crosses new boundaries. But even if a sufficient guarantee of safety could be reached, are there ethical problems?